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After investigating the behavior of ions during the growth of conductive filaments, we suggested a model for the growth process and electrical characteristics of the conductive filament under current-driven mode. In this model, the ionic displacement equation is derived by Arrhenius law, and a differential equation for the conductive filament growth has been established. We have also proved that the dielectric layer with the leakage current under current-driven mode can be equivalent to a parallel plate capacitor, which has a the equivalent dielectric constant. Consequently, the forming/set time of the device is gotten. At the same time, the kinetics process of ion motion is analyzed in detail, so that many microscopic parameters of the ion motion, such as the height of the potential barrier, the jump step, mobility and diffusion coefficient, can be obtained. Due to divalent and monovalent copper ions all participate in conduction, an equivalent copper ion Cuz+ is used for replacing both Cu+ and Cu2+, solving the computational complexity problem caused by multivalent metal ions. Finally, an equivalent circuit is proposed to calculate output voltage versus time characteristic. The calculation results of the model are consistent with experimental data. [ABSTRACT FROM AUTHOR]

Oxide-based memristors by incorporating thermally enhanced layer (TEL) have showed great potential in electronic devices for high-efficient and high-density neuromorphic computing owing to the improvement of multilevel resistive switching. However, research on the mechanism of resistive switching regulation is still lacking. In this work, based on the method of finite element numerical simulation analysis, a bilayer oxide-based memristor Pt/HfO2 (5 nm)/Ta2O5 (5 nm)/Pt with the Ta2O5 TEL was proposed. The oxygen vacancy concentrates distribution shows that the fracture of conductive filaments (CF) is at the interface where the local temperature is the highest during the reset process. The multilevel resistive switching properties were also obtained by applying different stop voltages. The fracture gap of CF can be enlarged with the increase of the stopping voltage, which is attributed to the heat-gathering ability of the TEL. Moreover, it was found that the fracture position of oxygen CF is dependent on the thickness of TEL, which exhibits a modulation of device RS performance. These results provide a theoretical guidance on the suitability of memristor devices for use in high-density memory and brain-actuated computer systems. [ABSTRACT FROM AUTHOR]

In this work, a compact model of the diffusive memristor is proposed from the perspective of the transition of electronic transmission mechanisms induced by the dynamics of the filament. First, a new physical model is established based on tunneling mechanisms that are used to fit the experimental data, and the results indicate that it is versatile enough for various diffusive memristors. In addition, the threshold voltage (V th) of the diffusive memristor negatively correlates with the ratio of ionic migration and the diffusion coefficient (u i /Ds), and the hold voltage (V h) positively correlates with the ratio of ionic diffusion and the migration coefficient (Ds/u i), which is useful for the selection of materials to achieve target electrical properties. Furthermore, the different parameters that influence the simulated switching curve are explored. The results indicate that the desired electrical characteristics can be obtained by adjusting these parameters. A compact electrical module model is then built and tested in LTspice to carry out bio-neuron and bio-synaptic performances completely. These simulations demonstrate that the model is reliable for exploring diffusive memristor applications. [ABSTRACT FROM AUTHOR]

In this work, a graphene (GR)/MoS2/GR selector was proposed based on first principle calculations. First, MoS2 was chosen as the resistive switching layer due to its high carrier mobility and was doped with nine kinds of dopants. Semiconductor characteristics were still maintained with P, Si, and Ti doping, while the others showed semimetallic properties. Then, heterostructures were built between metal GR and MoS·X (X = S, P, Si, Ti), and the conductivities of MoS·Si and MoS·Ti were obviously improved with the GR electrode through analysis of the impurity orbital contribution to the band energy. The plane average electrostatic potential and the charge density difference show that the Schottky barrier height and width of the GR/MoS·Si interface were the smallest and that the intensity of the built-in electric field was better than that of GR/MoS2 and GR/MoS·Ti. Finally, GR/MoS·X(X = S, Si, Ti)/GR selectors were proposed, and the electronic transmission shows that the ON-state current (Ion) and nonlinear coefficient of the GR/MoS·Si/GR selector were increased by two and three orders of magnitude, respectively, and the threshold voltage (Vth) was reduced by approximately 1 V, which can better suppress the leakage current in a one-selector one-RRAM cross array. This work may be instructive and valuable for the design and optimization of GR/MoS2/GR selectors. [ABSTRACT FROM AUTHOR]

Blue phosphorene (BlueP) has been widely researched recently as a potential material for novel photocatalytic and electronic devices. In this letter, due to its similar in-plane hexagonal lattice structure to MoS2, BlueP/MoS2 van der Waals heterostructures were built in six configurations. The II-stacking configuration was the most stable due to the lowest binding energy obtained from the calculation results. Furthermore, by controlling the external vertical strain, the geometry structures were optimized and the electronic structures of the BlueP/MoS2 heterostructure were modulated. We found that when the interlayer distance was 3.71 Ĺ, the structure was the most optimized. In addition, as the result of charge transfer at the interlayer, a built-in electric field was formed in the BlueP/MoS2 heterostructure, which explained the formation of the type-II band alignment structure. The optical properties results show that the BlueP/MoS2 heterostructure has a wide optical response range and good light absorption ability, which indicated significant potential for BlueP/MoS2 heterostructure use in the next generation of photovoltaic devices and water-splitting materials. [ABSTRACT FROM AUTHOR]